Elevators and spiders are typically arranged in alignment with an opening in the rotary table on the working platform of an oil well derrick. The elevator is used to hold, lower, and raise tubular pipe segments sometimes comprised of multiple lengths of pipe. The elevator is used to grip, lift, and release a pipe segment, in cooperation with the spider, with each pipe segment added to or removed from the pipe string in the well bore. Such pipe string may be a string of casing pipe, liner pipe, or drill pipe.
Each pipe segment typically has a threaded connection at each end with one end having an internally threaded band called a collar that protrudes or extends outward around the periphery of the pipe segment. The annular surface at the base of the collar between the outer periphery of the collar and the periphery of pipe is called the shoulder of the collar. An elevator supporting a pipe segment or a string of pipe segments on the shoulder of a collar is called a shoulder-type elevator.
An elevator and its components are subjected substantial stress, strain, and fatigue during use due to the repeated loadings from the weight of the pipe segments. Dropping a pipe segment can cause severe damage to rig equipment and injury to rig workers.
It would be an advantage to have an elevator designed with a minimum of components and with the components robustly configured to withstand the repeated loadings associated with continuous use in lifting and supporting the pipe segments to minimize failure and the cost associated with elevator replacement and repair. It would also be an advantage to provide an elevator that will safely secure a pipe segment within the elevator and minimize the steps needed for its use to enhance the safety of workers on the rig floor.